U.S. patent number 7,094,314 [Application Number 10/858,272] was granted by the patent office on 2006-08-22 for atmospheric pressure non-thermal plasma device to clean and sterilize the surfaces of probes, cannulas, pin tools, pipettes and spray heads.
This patent grant is currently assigned to Cerionx, Inc.. Invention is credited to Peter Frank Kurunczi.
United States Patent |
7,094,314 |
Kurunczi |
August 22, 2006 |
Atmospheric pressure non-thermal plasma device to clean and
sterilize the surfaces of probes, cannulas, pin tools, pipettes and
spray heads
Abstract
The present invention relates to methods and apparatuses for the
use of atmospheric pressure non-thermal plasma to clean and
sterilize the surfaces of liquid handling devices.
Inventors: |
Kurunczi; Peter Frank
(Weehawken, NJ) |
Assignee: |
Cerionx, Inc. (Pennsauken,
NJ)
|
Family
ID: |
33551829 |
Appl.
No.: |
10/858,272 |
Filed: |
June 1, 2004 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050005948 A1 |
Jan 13, 2005 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
60478418 |
Jun 16, 2003 |
|
|
|
|
Current U.S.
Class: |
156/345.44;
219/121.11; 156/345.48; 156/345.43 |
Current CPC
Class: |
B08B
7/0035 (20130101); B01L 13/02 (20190801); B08B
9/00 (20130101); A61L 2/14 (20130101); H01J
37/32825 (20130101); H05H 1/2406 (20130101); H05H
2277/10 (20130101); B01L 3/0244 (20130101); B01L
2300/0838 (20130101); B01L 3/021 (20130101); H05H
1/246 (20210501); H05H 1/2465 (20210501); G01N
35/1004 (20130101) |
Current International
Class: |
C23F
1/00 (20060101); B23K 15/00 (20060101) |
Field of
Search: |
;156/345.43,345.48,345.44 ;219/121.59,121.4,121.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
U Kogelschatz, "Dielectric-Barrier Discharges: Their History,
Discharge Physics and Industrial Applications," Plasma Chemistry
and Plasma Processing, vol. 23, No. 1, Mar. 2003. cited by other
.
U. Kogelschatz, "Filamentary, Patterned and Diffuse Barrier
Discharges," IEEE Transactions on Plasma Science, vol. 30, No. 4,
Aug. 2002. cited by other .
N. St. J. Braithwaite, "Introduction to Gas Discharges" Plasma
Sources Science and Technology, vol. 9, 2000, p517-527. cited by
other .
U. Kogelschatz et al. "Dielectric-Barrier Discharges, Principles
and Applications" J. Phys IV France, 7, 1997, C4-47. cited by other
.
E. M. Van Veldhuizen, W.R. Rutgers. "Corona Discharges:
Fundamentals and Diagnostics" Invited Paper, Proceedings of
Frontiers in Low Temperature Plasma Diagnostics IV, Rolduc, The
Netherlands, Mar. 2001, pp. 40-49. cited by other .
Publication ANSI/SBS 4-2004, "Well Positions for Microplates," Jan.
2004, The Society for Biomolecular Screening, www.sbsonline.com.
cited by other .
H. Conrads et al., "Plasma Generation and Plasma Sources" Plasma
Sources Science and Technology, vol. 9, 2000, p441-454. cited by
other.
|
Primary Examiner: Kornakov; M.
Attorney, Agent or Firm: Moser IP Law Group
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is entitled to priority pursuant to 35 U.S.C.
.sctn.119(e) to U.S. provisional patent application No. 60/478,418,
which was filed on Jun. 16, 2003. This application also claims
priority to International Application No. PCT/US2004/017223
entitled "Atmospheric Pressure Non-Thermal Plasma Device to Clean
and Sterilize the Surfaces of Probes, Cannulas, Pin Tools, Pipettes
and Spray Heads" by inventor Peter Kurunczi, filed on May 28, 2004.
Claims
What is claimed is:
1. Apparatus for plasma cleaning, comprising: a plate having a
conductive surface and an opposing dielectric surface, the plate
having a plurality of openings extending through the conductive and
dielectric surfaces; a plurality of hollow dielectric members
coupled at a first end to the dielectric surface of the plate and
extending in a direction opposite the conductive surface, each of
the plurality of hollow dielectric members having a first opening
at the first end aligned with a respective one of the plurality of
openings in the plate; and an electrode coupled to a central
portion of an outer surface of each of the hollow dielectric
members.
2. The apparatus of claim 1, wherein the conductive surface of the
plate further comprises an extension that protrudes into at least
one of the plurality of hollow dielectric members along an inner
surface thereof.
3. The apparatus of claim 2, wherein a distance measured along a
central axis of the at least one hollow dielectric member and
defined between a first end of the protruding extension of the
conductive member and a proximate edge of the electrode is greater
than or equal to zero.
4. The apparatus of claim 1, wherein the conductive surface is
grounded.
5. The apparatus of claim 1, wherein a central axis of each of the
plurality of hollow dielectric members are substantially
parallel.
6. The apparatus of claim 1, wherein the hollow dielectric member
is cylindrical.
7. The apparatus of claim 1, wherein the hollow dielectric member
is a polygonal tube.
8. The apparatus of claim 1, further comprising: a second opening
formed through at least one of the hollow dielectric members
proximate a second end of the hollow dielectric member opposite the
first end.
9. The apparatus of claim 8, wherein the second opening is fluidly
coupled to a negative pressure source adapted to draw plasma
cleaning byproducts through the second opening.
10. The apparatus of claim 1, wherein the plurality of hollow
dielectric members are arranged in a microliter plate format.
11. The apparatus of claim 1, further comprising a voltage source
adapted to provide a voltage between about 5000 V to about 15000 V
to the electrode.
12. The apparatus of claim 1, further comprising a voltage source
adapted to provide a voltage having a frequency between about 50 Hz
and about 14 MHz to the electrode.
13. The apparatus of claim 1, further comprising a closed end of at
least one of the hollow dielectric members opposite the first end.
Description
BACKGROUND OF THE INVENTION
Within the disciplines of the clinical, industrial and life science
laboratory, scientists perform methods and protocols with extremely
small quantities of fluids. These fluids consist of many categories
and types with various physical properties. Frequently, volumes are
worked with that are between a drop (about 25 microliters) and a
few nanoliters. There are a number of standard methods employed to
transfer liquid compounds from a source by aspirating the liquid
from such fluid holding devices into a fluid handling device having
a probe, cannula, pin tool or other similar component or plurality
of components which move, manually or robotically, and then
dispensing, from the same probe or plurality of probes, into
another fluid holding device.
Four common techniques are (1) a scheme using a probe or cannula,
that may or may not be coated with a layer of material or special
coating, which is attached directly or by a tube to a pumping
device, (2) a scheme using a disposable pipette instead of the
probe/cannula but otherwise similar, (3) a scheme using a spray
head with one or a plurality of openings and pumping system that
physically propels multiple precisely metered microdroplets, and
(4) a scheme using metal shafts with precisely machined hollowed
out spaces at their ends that hold the fluid by surface tension
(commonly referred to as a "pin tool").
As routine a process as fluid transfer is in the laboratory,
technical challenges remain to achieve suitable levels of
cleanliness of the dispensing devices. Currently the fluid handling
devices undergo a "tip wash" process wherein they are cleansed in
between use with a liquid solvent, such as DMSO or water. After the
"tip wash" process, the used and now contaminated liquids must then
be properly disposed of with respect to the required environmental
regulations. As an alternative to this wet "tip wash" process,
atmospheric pressure plasma can be used to replace the liquid
cleaning process with a "dry" plasma cleaning process, thus
eliminating the need for the handling and disposal of solvents that
are biohazards and environmentally unfriendly.
The term "plasma" is generally used to denote the region in an
electric gas discharge that has an equal number of positive ions
and negative electrons (N. St. J. Braithwaite, "Introduction to gas
discharges" Plasma Sources Science and Technology, V9, 2000, p517
527; H. Conrads et al., "Plasma Generation and Plasma Sources"
Plasma Sources Science and Technology, V9, 2000, p441 454). A
non-thermal, or non-equilibrium, plasma is one in which the
temperature of the plasma electrons is higher than the temperature
of the ionic and neutral species. Within an atmospheric pressure
non-thermal plasma there is typically an abundance of other
energetic and reactive particles, such as ultraviolet photons,
excited and/or metastable atoms and molecules, and free radicals.
For example, within an air plasma, there are excited and metastable
species of N.sub.2, N, O.sub.2, O, free radicals such as OH, NO, O,
and O.sub.3, and ultraviolet photons ranging in wavelengths from
200 to 400 nanometers resulting from N.sub.2, NO, and OH
emissions.
The "dry" plasma cleaning process is achieved by exposing the
surfaces of the fluid handling devices or other components to the
atmospheric pressure plasma. The above mentioned reactive and
energetic components can now interact with any contaminants on the
surfaces, thereby volatizing, dissociating, and reacting with the
contaminants, to form smaller and benign gaseous compounds that are
vented off through the plasma cleaning device.
In addition to removing various unwanted compounds, the plasma can
also be used to sterilize the surfaces of the fluid handling
devices. The same ultraviolet photons, especially those with
wavelengths below 300 nm, the free radicals and metastable
molecules, and the plasma electrons and ions, provide a very harsh
environment in which bacteria, viruses, fungi and their
corresponding spores are lysed or otherwise rendered non-viable and
either partially or completely volatized into gaseous
compounds.
SUMMARY OF THE INVENTION
In one embodiment, the present invention features an apparatus for
cleaning a fluid handling device. In one embodiment, the apparatus
includes an array of channels, each made of a dielectric material
and configured to accommodate a single fluid handling device, at
least one electrode in contact with each channel for producing a
discrete plasma in each channel, and at least one conducting ground
adjacent to the array of channels. In one aspect, an apparatus of
the invention has at least one conducting ground adjacent to each
of the channels. In another aspect of the invention, a fluid
handling device is the conducting ground. In yet another aspect, a
fluid handling device forms a conducting ground.
In an embodiment of the invention, a plasma is produced in a plasma
cleaning apparatus by applying a voltage in the range from about
5000 Volts to 15000 Volts.
In one embodiment of the invention, a channel of a plasma cleaning
apparatus is cylindrical. In another embodiment, a channel of a
plasma cleaning apparatus is rectangular. In one aspect of the
invention, a channel of a plasma cleaning apparatus is closed on
one end. In another aspect, a channel of a plasma cleaning
apparatus is open on both ends.
In one embodiment, the present invention features a plasma cleaning
apparatus that is in direct communication with a vacuum source.
In an embodiment of the present invention, an apparatus may contain
an array of plasma cleaning apparatuses. In one aspect, an array of
plasma cleaning apparatuses is in an arrangement corresponding to a
microtiter plate format.
In one embodiment, the present invention features a plasma cleaning
apparatus containing at least one rare gas.
In an embodiment, the present invention features an apparatus for
cleaning a fluid handling device, wherein the apparatus contains an
array of channels in a configuration corresponding to a microtiter
plate. In one embodiment, each channel includes a dielectric
material and is configured to accommodate a single fluid handling
device. In one aspect, there is at least one electrode in contact
with each channel for producing a discrete plasma in each channel
and, additionally, there is a continuous conducting ground adjacent
to the array of channels. In one embodiment, the channels of an
apparatus of the invention are cylindrical. In another embodiment,
the channels of an apparatus of the invention are rectangular.
The present invention also features, in one embodiment, an
apparatus for cleaning a fluid handling device, wherein the
apparatus contains an array of channels in a configuration
corresponding to a microtiter plate, further wherein each channel
consists of a dielectric material and is configured to accommodate
a single fluid handling device. In one aspect, there is at least
one electrode in contact with each channel for producing a discrete
plasma in each channel and additionally, there is a conducting
ground adjacent to each channel. In one aspect, a fluid handing
device forms the conducting ground for the channel in which the
device is accommodated. In one embodiment, the channels of an
apparatus of the invention are cylindrical. In another embodiment,
the channels of an apparatus of the invention are rectangular.
In an embodiment of the invention, a fluid handling device is
inserted into a channel of a plasma cleaning apparatus such that
the tip of the fluid handling device is located at about the center
of the plasma field.
In one embodiment, the present invention features a method of
cleaning a fluid handling device by positioning at least a portion
of a fluid handling device within the interior of a channel of a
plasma cleaning apparatus of the invention and forming a plasma
within the interior of each channel in order to clean the fluid
handling device. In one aspect, the invention features a method of
cleaning a plurality of fluid handling devices by positioning at
least a portion of each of a plurality fluid handling devices
within the interior of a discrete channel of a plasma cleaning
apparatus and forming a plasma within the interior of each of the
discrete channels to clean the plurality of fluid handling
devices.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated herein and
constitute a part of this specification, illustrate the presently
preferred embodiments of the invention and, together with the
general description given above and the detailed description given
below, serve to explain the features of the invention. Some aspects
of the drawings are not labeled, but are included to provide
further details of the invention. Further, in some drawings, if a
feature is present more than once in a drawing, the feature may be
referenced only once.
In the drawings:
FIG. 1 is a cross section view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention.
FIG. 2 is a top angle view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention.
FIG. 3 is a cross section view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention, wherein the
upper dielectric portion is extended perpendicularly outward.
FIG. 4 is a top angle view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention, wherein the
upper dielectric portion is extended perpendicularly outward.
FIG. 5 is a cross section view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention, wherein a
conducting surface is situated adjacent to the top of a
perpendicularly outward extended dielectric.
FIG. 6 is a top angle view of one embodiment of an atmospheric
pressure plasma-based cleaning device of the invention, wherein a
conducting surface is situated adjacent to the top of a
perpendicularly outward extended dielectric.
DETAILED DESCRIPTION OF THE INVENTION
In certain embodiments of the design of an atmospheric pressure
plasma device according to the present invention, a dielectric
barrier discharge (also known as a "silent discharge") scheme is
used, where at least one electrode to which an alternating voltage
is applied, includes an insulating dielectric (U. Kogelschatz et
al. "Dielectric-Barrier Discharges, Principles and Applications" J.
Phys IV France, 7, 1997, C4 47). The electrodes may comprise any
conductive material. In one embodiment, a metal may be used. Metals
useful in the present invention include, but are not limited to,
copper, silver, aluminum, and combinations thereof. In another
embodiment of the invention, an alloy of metals may be used as the
electrode. Alloys useful in the present invention include, but are
not limited to stainless steel, brass, and bronze. In another
embodiment of the invention, a conductive compound may be used.
Conductive compounds useful in the present invention include, but
are not limited to indium-tin-oxide.
In one embodiment, an electrode of the invention may be formed
using any method known in the art. In an embodiment of the
invention, an electrode may be formed using a foil. In another
embodiment of the invention, an electrode may be formed using a
wire. In yet another embodiment of the invention, an electrode may
be formed using a solid block. In another embodiment of the
invention, an electrode may be deposited as a layer directly onto
the dielectric. In one aspect, an electrode may be formed using a
conductive paint.
In an embodiment of the invention, a plasma is obtained in a
dielectric barrier discharge (DBD) when during one phase of the
applied alternating voltage, charges accumulate between the
dielectric surface and the opposing electrode until the electric
field is sufficiently high enough to initiate an electrical
discharge through the gas gap (also known as "gas breakdown").
During an electrical discharge, an electric field from the
redistributed charge densities may oppose the applied electric
field and the discharge is terminated. In one aspect, the applied
voltage-discharge termination process may be repeated at a higher
voltage portion of the same phase of the applied alternating
voltage or during the next phase of the applied alternating
voltage.
In another embodiment of the invention, a corona discharge scheme
may be used (E. M. van Veldhuizen, W. R. Rutgers. "Corona
Discharges: fundamentals and diagnostics" Invited Paper,
Proceedings of Frontiers in Low Temperature Plasma Diagnostics IV,
Rolduc, The Netherlands, March 2001, pp. 40 49). In one embodiment,
a corona discharge scheme may use asymmetric electrodes. In one
aspect of the invention, a discharge develops within a high
electric field region near the area of strongest curvature of a
sharp electrode. If the applied voltage or electrode gap distance
is such that the discharge cannot transverse the gas gap, then the
resulting corona discharge will be limited by electron
recombination and space charge diffusion. In one embodiment of the
invention, the tip of a probe, cannula or pin tool can serve as the
region of strongest curvature and resulting high electric field to
initiate a corona discharge.
Depending on the geometry and gas used for the plasma device, the
applied voltages can range from 500 to 20,000 peak Volts, with
frequencies ranging from line frequencies of 50 Hertz up to 20
Megahertz. In an embodiment of the invention, the frequency of a
power source may range from 50 Hertz up to 20 Megahertz. In another
embodiment of the invention, the voltage and frequency may range
from 5,000 to 15,000 peak Volts and 50 Hertz to 50,000 Hertz,
respectively. By way of a non-limiting example, such parameters of
voltage and frequency are commonly found in neon sign ballasts for
lighting purposes (Universal Lighting Technologies, Inc, Nashville,
Tenn.).
Dielectric materials useful in the present invention include, but
are not limited to, ceramic, glass, plastic, polymer epoxy, or a
composite of one or more such materials, such as fiberglass or a
ceramic filled resin (Cotronics Corp., Wetherill Park, Australia).
In one embodiment, a ceramic dielectric is alumina. In another
embodiment, a ceramic dielectric is a machinable glass ceramic
(Corning Incorporated, Corning, N.Y.). In one embodiment of the
invention, a glass dielectric is a borosilicate glass (Corning
Incorporated, Corning, N.Y.). In another embodiment, a glass
dielectric is quartz (GE Quartz, Inc., Willoughby, Ohio). In one
embodiment of the invention, a plastic dielectric is polymethyl
methacrylate (PLEXIGLASS and LUCITE, Dupont, Inc., Wilmington,
Del.). In yet another embodiment of the invention, a plastic
dielectric is polycarbonate (Dupont, Inc., Wilmington, Del.). In
still another embodiment, a plastic dielectric is a fluoropolymer
(Dupont, Inc., Wilmington, Del.). Dielectric materials useful in
the present invention typically have dielectric constants ranging
between 2 and 30.
The gas used in a plasma device of the invention can be ambient
air, pure oxygen, any one of the rare gases, or a combination of
each such as a mix of air or oxygen with argon and/or helium. Also
an additive can be added to the gas, such as hydrogen peroxide, to
enhance specific plasma cleaning properties.
FIG. 1 shows a cross section of a representative example of the DBD
plasma cleaning device. In one embodiment, a dielectric includes a
hollow open ended dielectric channel 101, with a thickness W from
about 0.5 mm to about 3 mm and a length L from about 1 cm to about
5 cm. Coupled to the outside of the dielectric is an electrode 102,
with an arbitrary thickness and a length I of about 0.5 to about 4
cm, which is connected to an AC power supply 104. The exact
dimensions of dielectric channel 101 are dependent on the
properties of the materials used for fabrication. In an embodiment
of the invention, the dielectric constant and dielectric strength
of a material may allow larger or smaller lengths and/or
thicknesses of such materials used in the present invention.
In one embodiment, a plasma cleaning device of the invention is
cylindrical. In another embodiment of the invention, a plasma
cleaning device is rectangular. In yet another embodiment, a plasma
cleaning device of the invention is elliptical. In still another
embodiment of the invention, a plasma cleaning device of the
invention is polygonal. Referring to FIG. 1, in one embodiment of
the invention, the end of a grounded fluid handling device 103 is
inserted into the dielectric channel to a point in between
electrode 102 at the midpoint of length I of electrode 102, and
acts as the opposing electrode. Plasma is thereby formed in between
the outer surface of the fluid handling device 103 and the inner
walls of the dielectric channel 101. In one embodiment, a plasma is
a dielectric barrier discharge plasma. In another embodiment, a
plasma is a corona discharge plasma. The free space H between the
top and bottom edges of electrode 102 and the top and bottom edges
of dielectric channel 101 is spaced a sufficient distance to
prevent arcing between electrode 101 and fluid dispensing device
103, which in this embodiment acts as a ground. In one embodiment,
the space is about 0.5 mm to about 10 mm to prevent arcing around
the dielectric. In one embodiment, the minimum dimensions of space
H may be determined as the distance required such that the
corresponding electric field circumventing dielectric 101, but
between electrodes 103 and 102, is not sufficient to induce a gas
breakdown directly between 103 and 102. It will also be understood
that the maximum dimension of space H may be determined by how far
the tip of fluid handling device 103 can be inserted into the
channel formed by dielectric 101.
Any volatized contaminants and other products from the plasma may
be vented through the bottom of the device by coupling the bottom
of the chamber formed by the dielectric to a region of negative
pressure. In one embodiment, a region of negative pressure is a
vacuum. In one aspect, a vacuum is in direct communication with a
channel of the plasma device and is used to draw plasma products
through the bottom of a plasma device of the invention.
FIG. 2 shows an embodiment of a representative DBD plasma cleaning
device with a plurality of dielectric barrier discharge structures,
with each individual plasma unit similar to that shown in FIG. 1.
Outer surface 203 of the individual dielectric channels 201 are all
coupled to a common outer electrode 202. In one embodiment,
electrode 202 is connected to an AC power supply. In another
embodiment of the invention, a power supply is a DC power supply.
In one aspect, a DC power supply is pulsed and employs a square
waveform. In another aspect, a DC power supply is pulsed and
employs a sawtooth waveform.
A plurality of grounded fluid handling devices can be inserted in
the plasma device and be simultaneously processed. The spacing
between each of the individual plasma devices within the plurality
are determined by the geometries of the fluid handling devices to
be inserted. Typical geometries for dielectric structure 201 can
follow those set by the Society for Biomolecular Engineering,
Microplate Standards Development Committee for 96, 384, or 1536
well microplates (Publication ANSI/SBS 4-2004, "Well Positions for
Microplates,", January 2004, The Society for Biomolecular Screening
<<www.sbsonline.com>>). Other geometries include single
opening units and openings in linear and two dimensional
arrays.
Several procedures may be used to clean or sterilize the inner and
outer surfaces of the fluid handling device. To clean, sterilize,
or otherwise process the inner surfaces, the reactive and energetic
components of the plasma are repeatedly aspirated into the fluid
handling device, using the fluid handling devices' aspirating and
dispensing capability, with the with aspiration volume, rate, and
frequency determined by the desired amount of
cleaning/sterilization required.
As shown in FIG. 1, in one embodiment of the invention, for
cleaning or sterilizing the outer surfaces of a fluid handling
device, the end of fluid dispensing device 103 can be inserted to a
position before or at the top of electrode 102 to just clean the
end of dispensing device 103, or it can be inserted to a position
further below the top level of electrode 102 to clean the outer
surfaces of the dispensing device. The period of time that the
plasma is on and the reactive and energetic components are in
contact with the surfaces is also determined by required processing
parameters.
In an embodiment of the present invention, the DBD plasma device
may have its upper dielectric portion extended perpendicularly
along Arrow A so that powered electrode 302 is also covered from
the top as shown in the representative cross section in FIG. 3.
This configuration allows the spacing J between electrode 302 and
dielectric 301 to be smaller than the spacing H for the preventing
of arcing around dielectric 301. In an embodiment of the invention,
the minimum dimensions of space J may be determined as the distance
required such that the corresponding electric field circumventing
dielectric 301, and between electrode 302 and electrode 303, here
the fluid handling device, is not sufficient to induce a gas
breakdown directly between 303 and 302. In one embodiment, the
maximum dimension of space J may be determined by how far the tip
of fluid handling device 303 is inserted into a plasma cleaning
device of the invention. In one embodiment of the invention, the
tip of a fluid handling device 303 is situated midway in a plasma
field. In another embodiment, the tip of a fluid handling device
303 is situated at about the center of a plasma field within a
plasma cleaning device of the invention. In one aspect, the tip of
a liquid handling device 303 is inserted into a plasma cleaning
device to the midpoint of electrode 302. In another aspect, the tip
of a fluid handling device 303 is placed within the region of
maximum plasma density. The thickness W of dielectric 301 is
similar to that discussed elsewhere herein with respect to FIG. 1.
Furthermore, there can be no spacing J, such that the top of
electrode 302 is adjacent to the bottom of perpendicularly extended
dielectric 301. This will result in a plasma being created when the
grounded fluid handling device is brought near to the top of
dielectric 301 but still outside the dielectric channel.
FIG. 4 illustrates an embodiment of the invention including a
plurality of DBD devices, each sharing a common extended upper
dielectric 401 which covers common electrode 402 from the top.
In another embodiment of the invention, a conducting surface 503 of
any thickness can be placed adjacent to the top of the
perpendicularly extended dielectric. FIG. 5 shows a cross section
of one embodiment of a representative design with a hole in
conducting surface 503 aligned with the opening in dielectric
surface 501. As shown in FIG. 5, inner edge M of conducting surface
503 can vertically cover inner dielectric wall 504 of dielectric
501 in addition to the top of the opening of dielectric 501. If
conducting surface 503 is grounded, a plasma can now be formed in
between the space K between the top of powered electrode 502 and
inner edge M of grounded electrode 503. Referring to FIG. 5, in one
embodiment of the invention, the maximum distance of space K may be
determined wherein the electric field between edge M of electrode
503 located within the channel formed by dielectric 501 and inner
dielectric wall 504 corresponding to the top of 502 is sufficient
to allow for gas breakdown and the formation of a plasma within the
channel formed by dielectric 501.
In one embodiment of the invention, the minimum distance of space K
may be zero. In another embodiment of the invention, the minimum
distance of space K may be a value greater than zero. The
optimization of space K facilitates the creation of a more uniform
and diffuse volumetric plasma inside the cylindrical channel formed
by dielectric 501 when a grounded fluid handling device is
inserted. In one embodiment of the invention, K is a distance
between zero mm and 20 mm. In one aspect, K is a distance between 1
mm and 10 mm. In an embodiment of the invention, K is about 3
mm.
In one embodiment of the invention, conducting surface 503 can be
left unconnected from ground by a switch so as to not have it
participate as an electrode during the plasma
cleaning/sterilization process. This will facilitate the creation
of a more concentrated plasma at the extreme end of the fluid
handling device as opposed to a diffuse volumetric plasma around
the end.
FIG. 6 illustrates one embodiment of the invention, featuring a
representative design of a plurality of DBD plasma devices sharing
a common conducting surface 603, which can be grounded or
ungrounded, and a common powered electrode 602, each separated by a
common perpendicularly extended dielectric 601.
In an embodiment of the invention, a plurality of DBD plasma
devices are arranged in a format of a microtiter plate. Examples of
microtiter plate formats include, but are not limited to, a 96-well
plate format, a 384-well plate format, and 1536-well plate format.
However, it will be understood that plate formats having fewer than
96 wells, such as 48-well, 24-well, 12-well and 6-well formats, are
also useful in the present invention. In one embodiment, the
physical properties of a channel useful in the present invention,
such as a channel formed by a well in a microtiter plate, can be
determined based on the properties of the dielectric material used,
the dimensions of such a channel, and the amount and character of
energy used to produce a plasma within such a channel, as described
in detail elsewhere herein. Similarly, the amount and character of
energy used to produce a plasma within a channel of the invention
may be determined, as described in detail elsewhere herein, by
analysis of the physical properties of such a channel and the
properties of the dielectric material used.
In an embodiment of the invention, an array of liquid handling
devices may also be in a format compatible with a microtiter plate.
In another embodiment, an array of liquid handling devices
compatible with a microtiter plate format may be cleaned using an
apparatus or method of the present invention. Microtiter plate
handling devices useful in the present invention include, but are
not limited to those using an XYZ format for liquid handling, such
as the TECAN GENESIS (Tecan, Durham, N.C.). Other microplate
handling formats compatible with the present invention include
those used with instruments such as the Beckman Coulter FX (Beckman
Coulter, Fullerton, Calif.) and the TekCel TekBench (TekCel,
Hopkinton, Mass.).
While the invention has been described in detail and with reference
to specific embodiments thereof, it will be apparent to one skilled
in the art that various changes and modifications can be made
therein without departing from the spirit and scope thereof. Thus,
it is intended that the present invention covers the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents. Further, each
and every reference disclosed herein is hereby incorporated by
reference in its entirety.
* * * * *
References